A filling device of this type has become known from the German patent application No. 29 51 665. On this system the conveying device moves each of the receptacles successively past several dosing units each of which meters a part of the bulk material to be filled in and after an intermediate filling into the weighing dish of a weighing unit, controlling the dosing unit, it transfers the material to the receptacle. Each of the dosing units is controlled by a timing circuit which determines the opening time for the flow of bulk material. The weighing unit itself controls the timing circuit of the pertaining dosing unit dependent on the specified tolerance limits. A signal memory adds for each of the receptacles the quantities of bulk material filled by the dosing units into the receptacle.
The expense of construction of the well-known system is relatively high. Several complete weighing and dosing units are necessary in order to be able to observe sufficiently narrow tolerances of the quantity of bulk material filled in. The tolerances are determined by the tolerance limits of the dosing unit, which is last in the charging course, and are so high that they are insufficient for many cases of application, especially for the filling of liquids. By means of the well-known system, merely solid bulk materials are therefore filled.
Furthermore there has been known the volumetric dosing and filling of liquids by means of piston pumps and the like. It is true, the well-known liquid filling systems are able to observe filling tolerances very accurately but they are relatively expensive with respect to construction. Beyond that, the dosing pumps are difficult to clean which causes problems especially in connection with the filling of sterile liquids. Moreover, the abrasion dust of the mechanically moved parts of the dosing pump increases the number of foreign particles in the liquid to be filled.